One of the principal problems encountered in the sale and use of litter for small animals, particularly cats, is suppressing the odor resulting from urine and feces buried and mixed with the litter as it is used daily by the animal. Since the litter, particularly for cats, is usually placed in a box, pan or the like, and is kept in the home where the cat will use it several times during the day, the waste creates an odor which permeates the room or other space where the container is located, and may create an unpleasant odor throughout the house. To eliminate the odor problem, odor masking or suppressant materials are often added to commercial litters in the form in which they are sold, and concentrated odor control preparations are available which can be added to the litter after the litter has been placed in the container for use by the cat. While some of these preparations used to mask or suppress odors are effective in varying degrees for a period of time, they diminish in effectiveness as the litter is exposed to the air in the container and may eventually become totally ineffective. One of the problems encountered in improving the odor suppressant or control products, and in determining the effectiveness of the products as they are used, is the lack of a means of establishing standards for comparison or even making a direct comparison among the various products available. Some products are exceptionally effective when initially released in the litter, while others are effective to a lesser degree over a longer period of time. Further, it has been difficult to determine the amount of odor control composition required to give optimum results for the normal period of use of the litter by the cat. Since the odor control compositions are generally relatively expensive, it is desirable not to add more of the material to the litter than the amount required to obtain satisfactory odor control for the normal use of the litter. This can only be accomplished reliably by testing and comparing the various compositions under normal or simulated normal conditions.